Good job of this haiku! I like the story it tells of the old myth of mermaids and ships sinking. I can picture her siting on a rock or something, singing sweetly as the ship sinks closeby. I like the idea of opposites here, she is calm and serene and they are frantically sinking. Nice.

I like too that you surprised us with the last line, the other two were all sweet and peaceful, and the last line certainly twists the whole image around. Good job